R. Roychoudhury et S. Panchanan, MODIFIED 1 N EXPANSION FOR THE DIRAC-EQUATION FOR SCREENED COULOMB POTENTIAL/, Zeitschrift fur Naturforschung. A, A journal of physical sciences, 48(11), 1993, pp. 1081-1085
It is shown that if one chooses the shift parameter correctly then the
lowest order term in the modified I/N expansion for the Dirac equatio
n as formulated by Stepanov and Tutik gives accurate results for Coulo
mb like potentials. Explicit eigenvalues have been obtained for the sc
reened Coulomb potential V(r) = -upsilon0/r[1 - rlambda(1 - 1/z)/(1 rlambda)] , and these are compared with exact numerical results and th
e results obtained by the choice of shift suggested by Stepanov and Tu
tik.